One prior-art surgical instrument for establishing circular coloanastomoses is known to comprise a cylindrical body having a mandrel at one of its ends and accommodating a coaxially arranged a rod which carries a circular knife held in place thereto, and is provided with a mechanism for its longitudinal traversing, a stem carrying a thrust head, and a mechanism for establishing circular anastomoses, said mechanism consisting of two members, of which one is mounted on the mandrel and the other, on the thrust head. Clearance between the members of the aforesaid mechanism required for applying a purse-string suture is adjustable by a screw-and-nut pair provided on the stem. The mandrel-mounted member of the mechanism for establishing circular anastomoses (hereinafter termed "circular anastomosing mechanism" for the sake of brevity), comprises a cylindrical bush accommodating a splined ring fixed in position thereon so as to define staple slots together with the inner surface of the bush. A cylinder-shaped staple ejector is also accommodated inside the bush. The surface of the thrust head facing the bush carries a plurality of staple recesses equispaced circumferentially thereon so as to correspond to the staple slots and serving to impart the B-shape to the staples in the course of suturing.
The application procedure of the above-discussed known instrument comprises introducing its working components into the lumen of the colon portions being stitched together and fixing the ends of the abovesaid colon portions on the stem of the surgical instrument between the two members of the circular anastomosing mechanism by tightening up preliminarily applied purse-string sutures. Then, both members of the circular anastomosing mechanism are brought together, whereupon the staples are driven out of the slots by the staple ejector and the circular knife longitudinal traversing mechanism, with the result that the staples pierce with their pointed legs the compressed colonic walls to get into the recesses and be bent into the shape of the letter B, thus firmly uniting the ends of the colon portions to be stitched together. Then the circular knife cuts a round hole in the colon within the suture.
Once the suture has been applied, the circular knife longitudinal traversing mechanism is returned to the initial position together with the staple ejector, the bush is disengaged from the thrust head by rotating the nut of the circular knife longitudinal traversing mechanism, and the instrument is withdrawn from the colon operated upon.
The known prior-art instrument discussed above is capable of applying different-diameter circular staple sutures by being provided with a set of changeable staple bushes, ejectors and knives, whereby the instrument is applicable to different-diameter colons whatever the depth of the operative field. However, metal staples left in the bulk of the colonic wall for a prolonged period of time contribute to ingress of infection from the colonic lumen into the bulk of colonic walls being sutured, which makes its way through the holes punctured by the staples. This, in turn, might be cause an inflammatory process resulting in a cicatricial constriction of the anastomotic lumen. In addition, a staple suture involves application of a serous ligature suture along the entire perimeter of the anastomosis so as to prevent propagation of infection and inflammatory process beyond the anastomosis established, which is fraught with peritonitis. Within a late postoperative period, metal staples left in the area of the anastomosis in prolonged contact with the colonic lumen favor the onset of a cicatricial stenosis of the established colostomy. Moreover, in some cases a staple suture fails to provide reliable hemostasis.